The present invention relates to a curable composition containing two or more curable polymers. More specifically, it relates to a curable composition that contains an acrylic acid ester based and/or methacrylic acid ester based curable polymer, and a curable oxyalkylene polymer, and which has superior mechanical properties, transparency, storage stability and weather resistance. In the following description, an acrylic acid ester and/or methacrylic acid ester is referred to as a (meth)acrylic acid ester.
The present inventors previously found that a (meth)acrylic acid ester based polymer having silicon-containing functional groups that are capable of crosslinking by forming siloxane bonds either at terminals or at side chains (these types of silicon-containing functional groups are hereinafter referred to as reactive silicon functional groups) crosslinks at normal temperatures by reacting with moisture, particularly moisture in the air, to form a network structure, thereby yielding a cured product having good properties such as high weather resistance, hardness nd water resistance. The present inventors completed an invention based on this finding and filed a Japanese patent application (OPI) No. 36395/79 ((OPI) is hereinafter intended to mean unexamined published Japanese patent application).
Oxyalkylene polymers having reactive silicon functional groups have been proposed in many patents such as U.S. Pat. Nos. 3,971,751, 3,979,384 and 4,323,488, Japanese Patent Publication Nos. 36319/70, 12154/71, 32673/74, and Japanese Patent Application (OPI) Nos. 156599/75, 73561/76, 6096/79, 82123/80, 123620/80, 125121/80, 131022/80, 135135/80 and 137129/80.
The prior art (meth)acrylic acid ester based polymers containing reactive silicon functional groups have superior performance but, on the other hand, the cured products thereof are brittle and even with resin compositions having low glass transition points, the cure products have poor tensile characteristics as manifested by low tensile elongation and a concurrently occurring significant decrease in strength.
The cured products of oxyalkylene polymers having reactive silicon functional groups possess superior tensile characteristics but there is still a need to achieve further improvements in their characteristics. In addition, all of the known oxyalkylene polymers having reactive silicon functional groups are defective in their performance i that because of the structure of the backbone chains and other factors, they do not possess satisfactory weather resistance and fail to produce an adequate bond with various adherends.
Several methods have been proposed as techniques that are capable of eliminating the defects of the prior art oxyalkylene polymers having reactive silicon functional groups. In the method disclosed in U.S. Pat. No. 4,593,068, an oxyalkylene polymer having reactive silicon functional groups is blended with a (meth)acrylic acid ester based polymer optionally, having reactive silicon functional groups. This method is effective to some extent in improving the initial performance of the oxyalkylene polymer having reactive silicon functional groups but it is not easy to obtain a sufficiently compatible composition having good transparency and good storage stability.
The present inventors found, s a sufficiently compatible composition containing an oxyalkylene polymer having reactive silicon functional groups and a (meth)acrylic acid ester polymer, a curable composition comprising:
(A) a copolymer that has reactive silicon functional groups and whose molecular chain consists substantially of;
(1) alkylacrylate ester monomeric units and/or alkyl methacrylate ester monomeric units, each having a short chain alkyl group with 1 to 8 carbon atoms; and PA0 (2) an alkyl acrylate ester monomeric unit and/or an alkyl methacrylate ester monomeric unit, each having a long chain alkyl group with at least 10 carbon atoms; and , PA0 (1) alkyl acrylate ester monomeric units and/or alkyl methacrylate ester monomeric units, each unit having an alkyl group of 1 to 8 carbon atoms; and PA0 (2)alkyl acrylate ester monomeric units an//or alkyl methacrylate ester monomeric units, each unit having an alkyl group of at least 10 carbon atoms; PA0 (i) a hydrolyzable organic silane monomer PA0 (wherein X is a hydrolyzable group. R.sup.1 is a monovalent organic group having 1 to 18 carbon atoms, n is an integer of 1 to 4, and each R.sup.2 or X can be the same or different when two or more R.sup.1 or X groups are attached), PA0 (ii) a partial hydrolysis condensate of the organic silane monomer represented by the general formula (I), and PA0 (iii) an orthoorganic acid ester represented by the general formula (II): EQU R.sup.2 C(OR.sup.3).sub.3 (II) PA0 (wherein R.sup.2 is a hydrogen atom or a methyl group, R.sup.3 is a monovalent organic group having 1 to 8 carbon atoms, and each R.sup.3 can be the same or different).
(B) an oxyalkylene polymer having reactive silicon functional groups (U.S. Ser. No. 07/112,979, now abandoned, and EPC Patent Application No. 87115834.1).
This composition has good transparency and good storage stability (even if the composition is stored for a long period of time separation into two layers and an increase in viscosity do not occur), because the compatibility between the oxyalkylene polymer and the (meth)acrylate polymer is sufficiently high. Furthermore the composition provides a cured product which has superior tensile characteristics, adhesion strength and weather resistance over those of the oxyalkylene polymer and the (meth)acrylate polymer.
An object of the present invention is to further improve the transparency and storage stability of a composition containing the oxyalkylene polymer and the (meth)acrylate polymer.